<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>php中文网(php.cn)</title>
</head>
<body>

<?php
/**
 * Created by IntelliJ IDEA.
 * User: XD
 * Date: 2017/8/22
 * Time: 18:13
 */
 function spamcheck($field){
    // filter_var() 过滤 e-mail
// 使用 FILTER_SANITIZE_EMAIL
$field=filter_var($field, FILTER_SANITIZE_EMAIL);

//filter_var() 过滤 e-mail
// 使用 FILTER_VALIDATE_EMAIL
if(filter_var($field, FILTER_VALIDATE_EMAIL))
{
return TRUE;
}
else
{
return FALSE;
}
 }


if (isset($_REQUEST['email'])) { // 如果接收到邮箱参数则发送邮件
// 判断邮箱是否合法
$mailcheck = spamcheck($_REQUEST['email']);
if ($mailcheck==FALSE)
{
echo "非法输入";
}
else
{
// 发送邮件
    $email = $_REQUEST['email'];
    $subject = $_REQUEST['subject'];
    $message = $_REQUEST['message'];
    mail("someone@example.com", $subject,
        $message, "From:" . $email);
    echo "邮件发送成功";
    }
} else { // 如果没有邮箱参数则显示表单
    echo "<form method='post' action='mailform.php'>
Email: <input name='email' type='text'><br>
Subject: <input name='subject' type='text'><br>
Message:<br>
<textarea name='message' rows='15' cols='40'>
    </textarea><br>
<input type='submit'>
</form>";
}
?>

</body>
</html>